National Climate Plans and Additional Scenarios

Scenarios:

National Plans – 3.3°C (6.0°F) – No change after national contribution pledge period.

<2.0°C Path – 1.8°C (3.3°F) – All countries peak by 2030 and then reduce steadily, with rates in the post-2030 period faster in the developed countries (5%/yr) than in the developing countries (3.5%/yr).

1.5°C Path – 1.5°C (2.8°F) – All developed countries peak by 2025 and then reduce steadily at 10%/yr; all developing countries peak no later than 2030 and then reduce steadily at 8%/yr.

Assumptions Behind the Scenarios:

In order to assess the cumulative impact of all the pledges and offer a projected temperature in 2100, we had to make some assumptions that are highlighted below. Many points are also explained in our FAQs.

We only include Nationally Determined Contributions (NDCs), Intended Nationally Determined Contributions (INDCs), and Long-Term Strategies submitted to the UNFCCC that are unconditional.

For the “National Plan” scenario, which is the one displayed on the Scoreboard, we assume no continued reductions by developed countries and no further action from developing countries beyond the timeframe of their plans. Specifically, there are four primary types of pledges, and we make the following assumptions for them:

Absolute reductions – For countries that are making absolute emissions reductions, we assume that emissions stay constant after 2025-2030 (the end of the pledge period), unless an NDC states otherwise. For example, Australia has offered to reduce their greenhouse gas emissions 26% below 2005 levels by 2030. After that, given there is no formal post-2030 pledge, we assume that Australia’s emissions do not increase nor continue to decrease, but stay constant at that new level.

Relative to a reference scenario – For countries that are reducing emissions from a reference scenario or business as usual (BAU) level, we assume they stay at the target level below the reference scenario after the pledge period. For example, Kenya has pledged to reduce their emissions 30% below their BAU by 2030. After 2030, we assumed that the emissions would continue to stay 30% below their Reference Scenario. Since the Reference Scenario is increasing, however, emissions increase at the same rate as the Reference Scenario.

Peaking – Emissions grow until year target peak year. For example, China has said they will peak their CO2 emissions by 2030. We assumed that the rate of growth in emissions would slow starting in 2015, approaching a flat trajectory gradually. After the peaking date, emissions would stay level. (Note: other greenhouse gas emissions continue to increase given they were not covered by China’s pledge).

Emissions intensity reduction – Change in emissions relative to the GDP of the country. For example, India reducing emissions intensity 40% (we took the low end of the pledge, which was 35-40%) by 2030. Up to 2030, we calculate emissions by using the GDP growth. After 2030, emissions intensity stays 40% below the growing GDP.

In the <2°C and 1.5°C scenarios, we assume continued action and reductions after the period when the current NDCs end.

The regional distribution of emissions reductions in the <2°C and 1.5°C scenarios is one representation of many possible approaches. We assume that developed countries move faster than developing countries.

We assume that proposals will be fully implemented, in accordance with the dates specified in the plans.

Some countries have made proposals for specific actions (rather than for emissions targets). If we don’t have a good estimate for the impact of those actions on emissions then we don’t include the action in our analysis.

We assume emission reductions cover all greenhouse gas emissions unless specified otherwise. In some cases for smaller countries, the structure of the model requires us to assume that they take proportional action on other greenhouse gases.

The C-ROADS reference scenario (also called “business as usual”) accounts for the UN’s medium fertility population projections, historical GDP per capita rates that converge over time to be consistent with other integrated assessment models, and GHG per capita projections for each gas that reflect trends over the last decade for CO2 and follow the IPCC’s RCP8.5 for the non-CO2 greenhouse gases.

C-ROADS uses a climate sensitivity of 3 (that is 3°C of temperature increase for a doubling of CO2 concentration.)

There are positive feedback loops in the real climate system that are not modeled in the current version of C-ROADS.

NDCs accounted for in “other developed” or “other developing” were calculated in accordance with that country’s percentage of emissions from the entire group. In other words, each nation’s proposals are scaled to their actual share of emissions within their bloc.

We are fortunate to have many colleagues in the field of adding up climate mitigation proposals to assess their sufficiency, aggregate their contributions, and see what more is needed. Explore other climate trackers.